Modified plating solution for plating and planarization and process utilizing same

ABSTRACT

A modified plating solution that can be used to electroplate a high quality conductive material that can be effectively polished and planarized includes (1) a solvent, (2) an ionic species of the conductive material to be deposited, (3) at least one additive to improve electrical and structural properties, and (4) a modifying agent.

[0001] This application claims the priority of provisional applicationSer. No. 60/182,100, filed Feb. 11, 2000, the entire disclosure of whichis incorporated by reference herein. Reference is hereby made to relatedapplication Ser. No. 09/472,523, filed Dec. 27, 1999, entitled WORKPIECE CARRIER HEAD FOR PLATING AND POLISHING, and Ser. No. 09/511,278,filed Feb. 23, 2000, entitled PAD DESIGNS AND STRUCTURES FOR A VERSATILEMATERIALS PROCESSING APPARATUS.

BACKGROUND AND SUMMARY OF INVENTION

[0002] Multi-level integrated circuit manufacturing requires many stepsfor metal and insulator film depositions followed by photoresistpatterning and etching or other means of material removal. Afterphotolithography and etching, the resulting wafer or substrate surfaceis non-planar and contains many features such as vias, lines, orchannels. Often these features need to be filled with a specificmaterial such as a metal, and then the wafer topographic surface needsto be planarized again, making it ready for the next level ofprocessing.

[0003] Electrodeposition is a widely accepted technique for thedeposition of a highly conductive material such as copper (Cu) into thefeatures on the semiconductor wafer surface. Chemical mechanicalpolishing (CMP) is then employed to planarize the resulting surface.

[0004] In FIG. 1a, the large feature 1 and the small feature 1 s areopened in the insulator layer 2, which is grown on a wafer. To fillthese features with Cu, a barrier or adhesive layer 3 is first depositedover the whole wafer surface. Then a conductive Cu seed layer 4 isdeposited over the barrier layer 3. Cu is electrodeposited over thewhole surface by (1) making an electrical contact to the barrier layer 3and/or the Cu seed layer 4; (2) placing the wafer in a standard Cuplating electrolyte; (3) placing an anode in the electrolyte; and (4)applying a negative voltage to the Cu seed layer with respect to theanode.

[0005]FIG. 1b shows the wafer after a short period of time which isadequate to deposit a Cu layer 5 with the thickness 5 a. As shown inFIG. 1b, the Cu layer of nominal thickness 5 a is adequate to fill inthe small feature is since there is Cu film growth even on theconductive vertical walls of this feature. The large feature 1, however,is still not filled with Cu. To fill the large feature 1, Cu platingneeds to proceed further, eventually yielding the structure depicted inFIG. 1c.

[0006] As can be seen in FIG. 1c, in this conventional approach, theelectrodeposited Cu layer 5 forms a very large metal overburden 6 on thetop surface of the insulator 2 and over the small feature is. Theoverburden 6 a over the large feature 1 is very small. The surface ofthe structure in FIG. 1c is non-planar, and therefore needs to bepolished and planarized. The overburden and portions of the barrierlayer 3 are customarily removed by CMP, yielding the structure in FIG.1d, which has electrically isolated Cu-filled features. Removal of thelarge and non-uniform metal overburden of FIG. 1c from the wafer surfaceis time consuming and expensive and is a major source of dishing defects6 b in large features.

[0007] It would be highly desirable if the plating process could yield aCu film which was planar and had a uniform overburden as depicted inFIG. 1e. CMP of such a substrate would be much faster and moreeconomical and defects would be minimized. If the plating process couldyield Cu-filled features with no overburden as depicted in FIG. 1f, thenthere would not be the need for CMP of the Cu layer. Only the portionsof the barrier layer 3 on the top surface of the insulator 2 would haveto be removed.

[0008] Electrodeposition is commonly performed in specially formulatedplating solutions or electrolytes containing ionic species of Cu as wellas additives that control the texture, morphology, and the platingbehavior of the Cu layer. A proper electrical contact is made to theseed layer on the wafer surface, typically along its circumference, andthe wafer surface is dipped in the plating solution. A consumable Cuanode or an inert anode plate is also placed in the electrolyte.Deposition of Cu on the wafer surface can then be initiated when acathodic potential is applied to the wafer surface with respect to theanode (i.e., when a negative voltage is applied to the wafer surfacewith respect to the anode plate).

[0009] There are many Cu plating solution formulations, some of whichare commercially available. One such formulation uses Cu-sulfate (CuSO₄)as the copper source. James Kelly et al., J. Electrochemical Society,vol.146, p. 2540-45 (1999). A typical Cu-sulfate plating solutioncontains water; Cu-sulfate; sulfuric acid (H₂SO₄); a small amount ofchloride ions; and a carrier, such as polyethylene glycols and/orpolypropylene glycols. Some other chemicals are then added to thissolution in small amounts to achieve certain properties of the Cudeposit. These additives can be classified under general categories suchas levelers, brighteners, grain refiners, wetting agents,stress-reducing agents, and the like.

[0010] Commonly used levelers and brighteners are generallysulfur-containing compounds, such as derivatives of thiourea. Otherlevelers and brighteners are sulfonic acid derivatives, such asmercaptobenzene sulfonate. Other brighteners include2,4-imidazolidine-diol, thiohydantoin, polyethers, polysulfides, andvarious dyes. There is a large volume of literature on the additives forCu-plating solutions and their influence on the electroplated deposits.For example, U.S. Pat. No. 4,430,173 discloses an additive compositioncomprising the sodium salt of ω-sulfo-n-propylN,N-diethyldithiocarbamate and crystal violet, which shows excellentstability. U.S. Pat. No. 4,948,474 discloses a brightener additive for aCu plating solution. U.S. Pat. No. 4,975,159 discloses lists ofalkoxylated lactams and sulfur-containing compounds which were found tobe effective additives. U.S. Pat. No. 3,328,273 describes Cu platingbaths containing organic sulfide compounds.

[0011] Although a large volume of literature exists on the subject ofadditives to Cu plating solutions, many of the additive formulations arekept as trade secrets by plating solution suppliers. Some examples of Cuplating additive solutions provided commercially are: (1) CUBATH M®system, marketed by Enthone-OMI; (2) COPPER GLEAM® system, marketed byLeaRonal; and (3) ULTRAFILL® Addition agent and Suppressor, marketed byShipley. Commercially available Cu plating solutions with additivestypically yield bright and soft Cu deposits that have low stress. Copperlayers deposited out of these solutions cannot be polished andplanarized with the same solution, simply because the plating solutionsare formulated only for plating, not for polishing or planarization.

[0012] Copper layers are traditionally polished and planarized by CMP ina machine specifically designed for polishing. In this method, theplated wafer is loaded onto a carrier head. The wafer surface coveredwith the non-planar Cu deposit (FIG. 1c) is brought into contact with apolishing pad and a polishing slurry. The polishing slurry containsoxidizing chemicals and micron or sub-micron size abrasive particles.When the pad and the wafer surfaces are pressed together and moved withrespect to each other, polishing by the abrasive particles is initiatedand the metal overburden is removed from the surface. A different CMPslurry is used to remove the barrier layer from the top surface of theinsulator. The desired planar surface with electrically isolatedCu-filled features shown in FIG. 1d is eventually obtained.

[0013] The chemistry of the polishing slurry and the type of theabrasive particles used in a given CMP process are selected according tothe chemical nature of the material to be removed. Therefore, thecompositions of the polishing slurries for copper, tungsten, tantalum,tantalum nitride, silicon dioxide, and like materials that are used inintegrated circuit (IC) manufacturing may all be different. For example,U.S. Pat. Nos. 4,954,142; 5,084,071; 5,354,490; 5,770,095; 5,773,364;5,840,629; 5,858,813; 5,897,375; 5,922,091; and 5,954,997, all disclosevarious CMP slurry compositions for effective polishing of Cu. Slurriestypically contain a solvent and a selection of abrasive particles, suchas silica or alumina particles, which are suspended in the solvent.Furthermore, complexing agents such as NH₃ and/or oxidizing agents suchas NO₃ ⁻ and Fe(CN)₆ ³⁻ are also included in the formulations toincrease the dissolution rate of the abraded material and thus increasethe Cu removal rate.

[0014] A typical CMP slurry has a high pH so that a passivating surfacelayer can be formed and sustained on Cu surfaces in the features wherethe pad cannot make high pressure contact. The surface layer over the Cufilm protects Cu in such areas from chemical attack by the solution.High regions of the Cu layer making high pressure physical contact withthe pad get polished because the abrasive particles can remove thepassivating surface layer. The abraded material is then carried awayfrom the wafer surface and dissolved by the slurry.

[0015] As discussed in J. Steigerwald et al., CMP of MicroelectronicMaterials, sections 7.2.1. and 7.2.2., John Wiley & Sons Inc. (1997), Cuis not expected to form a protective surface film in acidic solutionswith low pH. Therefore, if an acidic slurry is employed for CMP, Cu inall regions, including in the recessed features, would dissolve into theacidic slurry and planarization as depicted in FIG. 1e would not bepossible. In CMP of Microelectronic Materials, it is suggested that whenusing an acidic CMP slurry, a non-native, film-forming agent such asbenzotriazole (BTA) may be added to the slurry composition to avoidchemical etching of the deposit in the recessed areas. However, the datain CMP of Microelectronic Materials also demonstrates that BTA mayreduce the polishing rate.

[0016] According to CMP of Microelectronic Materials, during CMP, aprotective layer such as an oxide layer first forms on the Cu surfacedue to the chemical composition and the pH of the slurry. The surfacefilm is then efficiently removed by the mechanical action of theabrasive particles. Removed material is moved away from the vicinity ofthe wafer surface to avoid re-deposition. This process continues untilall the metal on high surfaces making contact with the pad is removed.CMP slurries that are commercially available are all designed forpolishing and planarization only. There is no CMP slurry formulationthat allows plating of materials.

[0017] Thus, the chemical compositions of metal plating solutions andmetal polishing and planarization slurries are very different. Polishingcannot be realized in prior art metal plating solutions, and platingcannot be achieved with standard CMP slurries. This is not customarily aproblem since metal plating and CMP processes are carried out indifferent machines at different times, and the plating solutions and CMPslurries used in these machines are only expected to achieve theirrespective single functions, namely, deposition and polishing. However,this conventional approach is time consuming and it raises themanufacturing cost for integrated circuits.

[0018] It is an object of the present invention to provide a metaldeposition solution that allows for polishing and planarizing the platedmetal layer using the same solution. Metal layers deposited andplanarized using such a solution would yield desirable flat surfaces asshown in FIG. 1e in a short period of time and would even achieve thestructure depicted in FIG. 1f using a single machine. The idea ofsimultaneous plating and polishing or plating/polishing of a conductingmaterial on a workpiece or wafer surface was disclosed in co-pendingU.S. patent application Ser. No. 09/201,929, filed on Dec. 1, 1998, theentirety of which is incorporated herein by reference.

[0019] U.S. Pat. No. 6,004,880 discloses a modified CMP apparatus andtechnique to achieve simultaneous plating and polishing on asemiconductor wafer. However, compositions of solutions that can besuccessfully employed in such processes have not been fully disclosed.U.S. Pat. No. 6,004,880 discloses a modified CMP apparatus and asimultaneous plating/polishing technique that would be achieved bymodifying a CMP slurry. In other words, the approach is modifying a CMPprocess to also do plating. Therefore, an electrolyte composition thatmight contain Cu-sulfate was proposed to be mixed into a CMP slurry.Such an approach of mixing plating electrolytes into polishing slurrieshas several drawbacks.

[0020] Electronic applications of electroplated metals, such aselectroplated Cu, require not only planar surfaces, but also excellentelectrical and mechanical properties. Copper films used in suchapplications should have low resistivity values close to the bulkresistivity of Cu, which is about 1.6×10⁻⁶ ohm-cm. Films should alsohave good electromigration properties; should adhere well to theirsubstrates; and should have large grains. Although planarization isimportant in the overall process, a highly planar Cu layer with highresistivity would not be usable in many integrated circuit applicationswhere high performance is desired, because the limiting speed at whichthe circuit can be run is a strong function of the resistivity of themetal used in its structure. Copper is typically plated out of acidicelectrolytes because layers obtained from these electrolytes have lowresistivity and other desirable characteristics. Plating Cu out of asolution with large amounts of undesirable impurities typicallydeteriorate the properties of the deposited films. Therefore, thequality of Cu layers obtained from slurry/electrolyte mixtures would inall probability be poor.

[0021] Mixing plating solutions into CMP slurries to modify the slurriesfor plating would be also problematic for other reasons. The chemistryof plating solutions and polishing slurries are highly incompatible. TheCu-sulfate plating solutions that are commonly used for Cu plating arehighly acidic solutions with pH values well below 0.5, typically below0.1. High pH values deteriorate the plated film properties, typicallygiving rise to rough and/or burned deposits, especially at high platingcurrent densities that are necessary for fast processing. Thisdeterioration is because limiting current density values decrease as thepH of the solution goes up. In contrast, CMP slurries that are commonlyused have pH values well above 2, typically above 4.0. For example, CMPslurries CPS-01 and CPS-03 sold by 3M® corporation have pH values ofaround 7. HASTILITE® marketed by Rhodes has a pH of 7.25. MICROPLANARCMP 9000® by EKC Technology Inc. has a pH value of 8.83. As discussed inCMP of Microelectronic Materials, high pH is desirable in CMP slurriesbecause it allows the formation of a protective surface layer on Cu. Inacidic electrolytes with low pH values, surface layers such as Cu-oxidescannot be stable. It is therefore expected that mixing low pH platingsolutions with high pH polishing slurries would have detrimental effectson both plating and polishing processes.

[0022] Slurries are formulated to keep their abrasive particlesdispersed or in suspension. According to the basic theory ofdispersions, dispersion characteristics of small particles in a solutionsuch as a CMP slurry is a strong function of the pH of the solution.Changing the pH of a perfect dispersion may totally destroy thatdispersion and cause the particles to agglomerate and precipitate out.Plating is also sensitive to pH changes and is affected by theelectrolyte composition. Even parts per million (ppm) levels ofimpurities/additives in plating solutions have profound effects on theproperties of the plated materials. Electronic applications ofconductive materials such as Cu require deposition of good quality filmswith low resistivity and large grain. Chemicals in the polishing slurrywould affect the quality of the plating solution and therefore thequality of the Cu layer that might be plated with an electrolyte/slurrymixture.

[0023] U.S. Pat. No. 6,004,880 discloses the idea of adding a platingsolution to modify a polishing slurry for the simultaneousplating/polishing of Cu on a wafer with surface feature widths ofpreferably 1 micron or less. In many circuit designs, however, there aresurface features with widely varying widths. The small feature in FIG.1a, for example, may have a width of only 0.1-0.5 microns, whereas thewidth of the large feature may be 10-100 microns. The depth of thefeatures may be in the range of 1-5 microns. A slurry/electrolytemixture could be introduced onto a wafer surface with only submicronsize features, if the particle size in the slurry is selected such thatthe particles are larger than the feature size. This way, the largeparticles cannot get into the wells or channels defined by the smallfeatures. However, if there are both large and small features on thewafer, then use of such a slurry would result in lodging of some of theabrasive particles into the large vias and channels. The lodgedparticles would then interfere with Cu plating into the features;increase resistivity; destroy microstructure and device performance; anddrastically reduce the process yield.

[0024] Even if the plating solution and the CMP slurry could be mixedand used for plating and polishing, their recycling would beuneconomical. Once used, these solutions would have to be discarded andthe cost of processing would be high.

[0025] The present invention solves these problems by modifying aplating solution for plating and planarization, rather than modifying apolishing slurry for polishing and plating as disclosed in the priorart.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIGS. 1a through 1 d show an example of a prior art procedure forfilling wafer surface features with electrodeposited Cu, and thenpolishing the wafer to obtain a structure with a planar surface andelectrically isolated Cu plugs or wires;

[0027]FIG. 1e shows a metal deposit with uniform metal overburden acrossthe surface of the substrate according to the present invention;

[0028]FIG. 1f shows plating just in the holes according to the presentinvention; and

[0029]FIG. 2 schematically shows a plating/polishing apparatus that canbe used according to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0030] The present invention modifies a plating solution for plating andplanarization due to the following factors.

[0031] The quality of the deposited metal layer is of prime importance.In any process, one has to first assure this quality. Therefore, insteadof taking a polishing solution and adapting it for plating, we took theroute of taking a well-formulated plating solution and modifying it byadding a modifying agent to achieve in-situ planarization of the platedmetal. The conditions to be satisfied by the modifying agent are: (1)addition of the modifying agents into the plating solution should notaffect the grain size and resistivity of the plated layer in adetrimental way; (2) the modified plating solution containing modifyingagents should yield a plated layer that can be efficiently polished andplanarized; and (3) a user should be able to easily monitor the amountof the modifying agents in the solution and re-furbish and recycle theused solution in a closed loop system.

[0032] The present invention discloses plating solution compositionsthat are modified to allow the deposition of a high quality Cu layer,and at the same time allow either simultaneous or sequential polishingand planarization of the deposited layer. In this approach, commerciallyavailable, highly acidic Cu plating solutions are modified by theaddition of oxidizers which do not appreciably affect the pH of thesolution or the quality of the plated Cu layer. No slurry or particlesare included in the formulation. Polishing and planarization is achievedusing a fixed abrasive pad.

[0033] A version of a plating/polishing apparatus that can be used topractice the present invention is schematically shown in FIG. 2. Thecarrier head 10 holds the wafer 16 and at the same time provides anelectrical contact 7 to the seed layer on the wafer surface. The headcan be rotated around a first axes 10 b. It can also be moved in x, y,and z directions. A fixed abrasive polishing pad 8 is placed on an anodeassembly 9 across from the wafer surface. Modified plating solution 9 aof the present is supplied to the wafer surface, preferably through theopenings in the anode assembly and the pad as shown by the arrows in thefigure. The solution then flows over the edges of the pad into thechamber 9 c to be re-circulated after cleaning/filtering/refurbishing.An electrical contact 9 d is provided to the anode assembly 9. The anodeassembly 9 can also be rotated around the axes 10 c. The gap between thewafer surface and the pad is adjustable by moving the carrier headand/or the anode assembly in the z direction. When the wafer surface andthe pad are touching, the pressure that is exerted on the two surfacescan also be adjusted.

[0034] For plating, a potential is applied between the electricalcontact 7 to the wafer 16 and the electrical contact 9 d to the anodeassembly 9, making the wafer surface more negative than the anodeassembly. Under applied potential, a high quality layer of metal platesout of the modified plating solution onto the wafer surface. Byadjusting the gap between the pad and the wafer surface and/or byadjusting the pressure with which the pad and the wafer surface toucheach other, one can achieve just plating, or plating and polishing. Forexample, if there is a gap between the wafer surface and the pad,plating is expected to take place over the whole wafer surface asillustrated in FIG. 1c. In this case, a metal film is obtained that canbe polished in a CMP process in a separate CMP machine. It should benoted that Cu layers plated out of the modified plating solutions of thepresent invention were found to be polished more efficiently compared toCu layers obtained from standard plating solutions and therefore areadvantageous.

[0035] If the pad and the wafer surface in FIG. 2 were touching at lowpressures, then plating can freely take place in the holes in thesubstrate where there is no physical contact between the wafer surfaceand the abrasive pad, but the plating rate will be reduced on the topsurfaces where there is physical contact between the pad and thesurface. The result is a metal deposit with uniform metal overburdenacross the surface of the substrate as shown in FIG. 1e. This is incontrast to the conventional deposition method of FIG. 1c where there issignificant variation in metal overburden across the substrate. If thepressure with which the substrate and the pad surfaces touch each otheris further increased, it is possible to obtain plating just in the holesas shown in FIG. 1f. In this case, the increased polishing action on thehigh points of the substrate surface does not allow accumulation ofmetal layer on these regions.

[0036] It should be understood that the modified plating solution of thepresent invention may be used in apparatus with various other designs,including designs for just plating and designs for plating andpolishing. For plating a metallic layer that can be later polished moreeffectively, many kinds of plating apparatus can employ the solution ofthis invention by simply replacing the standard plating solution withthe modified solution of the present invention. For plating/polishingapplications, any apparatus that can apply a voltage difference betweenthe wafer surface and an electrode touching the modified platingsolution of the present invention, while pressing a fixed abrasive padagainst the wafer surface and moving the pad and the wafer surface withrespect to each other, can be employed.

[0037] It is not fully understood how the addition of small amounts ofoxidizers in the highly acidic Cu plating solutions allows the use ofthese solutions for plating and planarization. However, it is possiblethat the surface layer formed on the Cu deposit by the presence ofoxidizers does not interfere with the plating of a good quality Culayer, but at the same time can be efficiently removed from the sectionsof the film where the pad contacts it with some pressure.

[0038] The amount of oxidizer added to the plating solution may be lessthan 500 ppm, however preferably it should be more. Oxidizerconcentration may typically be in the 0.01 wt. % to 10 wt. % range. Bothinorganic and organic oxidizers, either pure or mixed, or their mixturescan be used as modifying agents, but organic oxidizers are preferred.Among the many organic oxidizers known to those in the field ofchemistry, the preferred modifying agents are organic nitrites andnitrates. Although butyl nitrite is an organic oxidizer that was used asthe modifying agent in the following examples to demonstrate the presentinvention, other modifying agents can also be used to obtain the sameresult. For example, other organic oxidizers, preferably organicnitrites can be used. Organic nitrites include, but are not limited to,alkyl nitrites, aromatic nitrites, and polyaromatic nitrites. Alkylnitrites include, but are not limited to, primary, secondary andtertiary compounds of methyl, ethyl, propyl, butyl, and amyl nitrites.Additionally, nitrates of the above compounds may also be used.

[0039] Although the examples use Cu deposits, it should be understoodthat many other conductive materials such as Cu alloys, W, Au, Ni, Pt,Pd, Ag, Co, Sn, Pb and their alloys can be used in the practice of thepresent invention.

EXAMPLES Example 1 Standard Plating Solution

[0040] A Cu-sulfate based Cu plating solution was prepared as follows:

[0041] 70 grams per liter of CuSO₄+SH₂O, 150 grams per liter ofconcentrated H₂SO₄, and 70 ppm per liter of Cl- ions were mixed inenough water to make 10 liters of solution. Twenty-five ml of UltrafillS2001®, 1.0 ml of Ultrafill A2001® from Shipley were then added toobtain a standard good quality plating electrolyte.

[0042] This solution was used for Cu plating on a 200 mm diameter wafersurface using the apparatus of FIG. 2. The wafer surface containedsub-micron size features as well as features in the 10-100 micron range.The pad was a fixed abrasive pad supplied by 3M® company. The diameterof the pad was 180 mm and the anode assembly was oscillated in thehorizontal direction so that plating could be achieved on all areas onthe larger wafer surface. During plating, the distance between the padand the wafer surface was kept at around 0.1 cm. The plating current was2 Amp and the plating solution flow was 5 liters/minute. The wafer wasrotated at 75 rpm and the anode assembly with the pad was rotated at 100rpm in the same direction. Several wafers were plated for times rangingfrom 90 seconds to 4 minutes. Resulting Cu deposits were similar to theones depicted in FIGS. 1b and 1 c depending on the depth of the surfacefeatures and the plating period. The Cu deposits after aging at roomtemperature for one day had a resistivity of below 2×10⁻⁶ ohm-cm,indicating good material quality.

Example 2 Polishing and Planarization Using Standard Plating Solution

[0043] The plating experiment of Example 1 was repeated, except thistime, after an initial period of 30 seconds, the pad was pushed againstthe wafer surface at a pressure of 1 psi for plating as well aspolishing and planarization. The resulting Cu deposit had a roughsurface with deep scratches apparently caused by the abrasive pad. Therewere also Cu particles smeared all over the surface of the wafer. Verylittle amount of material removal was achieved because material removedfrom one region of the surface by the action of the abrasive pad wasprobably deposited back onto the surface at another region in the formof smeared particles, which were welded or bonded to the substratesurface. The substrate defect level was extremely high and featurefilling was poor.

Example 3 Modified Plating Solution According to the Present Invention

[0044] Five ml per liter of butyl-nitrite was added as a modifying agentto the electrolyte of Example 1 and the plating and polishing experimentof Example 2 was repeated using this modified plating solution. Theresulting Cu deposit was highly planar and was similar to the structureshown in FIG. 1e. Copper layer resistivity was still below 2×10⁻⁶ohm-cm, demonstrating the ability of the modified electrolyte to yieldhigh quality Cu deposits. Copper film was planar with uniform overburdenover the sub-micron size features as well as the large features.

[0045] The foregoing disclosure has been set forth merely to illustratethe invention and is not intended to be limiting. Since modifications ofthe disclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. A process of depositing and simultaneouslypolishing and planarizing a high quality conductive layer on a surfaceof a substrate, comprising: loading a substrate on a holder; applyingelectrical power to the surface of the said substrate; introducing aplating solution comprising an oxidizer on an abrasive polishing pad;pressing the abrasive polishing pad against the surface of saidsubstrate; contacting the plating solution with the surface of thesubstrate and a second electrode; applying a potential differencebetween the surface of the substrate and the second electrode;depositing a conductive layer on the surface of the substrate; andmoving the abrasive pad and the surface of the substrate with respect toeach other, thereby simultaneously polishing and planarizing theconductive layer on said substrate.
 2. A process according to claim 1,wherein the conductive layer comprises copper.
 3. A process according toclaim 1, wherein the plating solution comprises an acidic copper platingsolution.
 4. A process according to claim 3, wherein the acidic copperplating solution has a pH value of less than
 4. 5. A process accordingto claim 1, wherein said oxidizer is selected from the group consistingof an inorganic oxidizer, an organic oxidizer, and mixtures thereof. 6.A process according to claim 5, wherein the oxidizer is an organicnitrite.
 7. A process according to claim 6, wherein the nitrite isselected from the group consisting of alkyl nitrites, aromatic nitrites,and polyaromatic nitrites.
 8. A process according to claim 7, whereinthe organic nitrite is an alkyl nitrite.
 9. A process according to claim8, wherein the alkyl nitrite is butyl nitrite.
 10. A process accordingto claim 1, wherein the oxidizer is an organic nitrate.
 11. A processaccording to claim 1, wherein the substrate comprises surface featureshaving a width of about 10-100 microns.
 12. A modified plating solutionfor simultaneous polishing and planarization of a substrate, comprising:a solvent; an ionic species of a conductive material; and an oxidizer.13. A modified plating solution according to claim 12, wherein saidoxidizer is selected from the group consisting of an inorganic oxidizer,an organic oxidizer, and mixtures thereof.
 14. A modified platingsolution according to claim 12, wherein said oxidizer is an organicnitrite selected from the group consisting of alkyl nitrites, aromaticnitrites, and polyaromatic nitrites.
 15. A modified plating solutionaccording to claim 12, wherein said solution has a pH value of less than4.
 16. A modified plating solution according to claim 12, wherein saidoxidizer is present in an amount of more than 500 ppm.
 17. A modifiedplating solution according to claim 12, wherein said oxidizer is presentin an amount of 0.01 to 10 wt. % of said solution.
 18. A modifiedplating solution according to claim 12, wherein said conductive metal isCu.
 19. A modified plating solution according to claim 12, wherein saidconductive metal is selected from the group consisting of W, Au, Ni, Pt,Pd, Ag, Co, Sn, Pb and their alloys.
 20. A modified plating solutionaccording to claim 12, further comprising at least one additive selectedfrom the group consisting of levelers, brighteners, grain refiners,wetting agents, and stress-reducing agents.